Ultraviolet Light Stimulation Research Articles

Construction of photocatalytic coating for alleviating the shriveling of postharvest fruit cucumber after simulated transportation

The shriveling of fruit cucumber was commonly occurred during supply chain, photocatalyst exposed to UV light can endow the coatings with ethylene removal capacity to reduce the respiration of fruit and water loss. The study developed a novel photodynamic technology responsive photocatalytic coating with exceptional ultraviolet (UV) photocatalytic degradation of ethylene ability to decay the shriveling of postharvest fruit cucumber during supply chain. This coating involved the integration of Carbon dots (CDs)-loaded nano ZnO and the skillful selection of pullulan (Pul) and apple pectin (AP) matrix. The CDs/ZnO coatings boasted an impressive array of photocatalytic degradation of ethylene and adhesion properties, including high ethylene removal rates of 32.04 % in 60 min UV light stimulation. The decrease of cell-wall strength, degradation of the cell wall polysaccharides and water loss resulted in cucumber shriveling. Compared with CK sample, after UV-CDs/ZnO coating treatment, the higher firmness and cell wall polysaccharides were found in cucumbers with lower cell wall degrading enzymes activities, weight loss and water movement, which was associated with the decrease of respiration and ethylene accumulation. The UV-CDs/ZnO coatings possessed promising potential for alleviating the shriveling of postharvest fruit cucumber and applications in fruits preservation in the future.

UV-Light-Induced Morphological Transformation of Spiropyran Assemblies from Irregular Sheet-like Structures to Nanospheres.

Studies on self-assembling systems with a controllable morphology responding to light stimulation are significant for revealing the process and mechanism of assembly. Here, a molecule of spiropyran derivative (SP) possessing photoresponsive assembly morphology is constructed. SP self-assembles into irregular sheet-like structures whose morphology can be significantly transformed into regular nanospheres under continuous ultraviolet light stimulation. The UV-vis absorption spectra indicate that 56% of SP are isomerized from closed-ring form (SPC) to open-ring form (SPO) with color changes from colorless to magenta. Furthermore, theoretical calculations demonstrate that SPO-SPO aggregates possess stronger van der Waals forces than do SPC-SPC aggregates and tend to form stable intermediates combined with SPO isomers. Therefore, the isomerization of SP from SPC to SPO and the differences in intermolecular interactions are important factors in the morphological transition. Our study provides an efficient strategy to modulate the assembled morphology, which holds great promise to be applied in the field of smart materials.

Light‐controlled switchable underwater adhesive

AbstractDespite extensive efforts in designing and preparing switchable underwater adhesives, it is not easy to regulate the underwater adhesion strength locally and remotely. Here, we design and synthesize photoreversible copolymer of poly[dopamine methacrylamide‐co‐methoxyethyl‐acrylate‐co‐7‐(2‐methacryloyloxyethoxy)‐4‐methylcoumarin]. Due to the dynamic formation and breaking of chemical crosslinking networks within the smart adhesives, the material shows widely tunable adhesion strength from ∼150 to ∼450 kPa and long‐range reversible maneuverability under orthogonal 254 and 365 nm ultraviolet light stimulation via the coumarin dimerization and cycloreversion. Moreover, the adhesive exhibits good circulation performance and stability in an acid–base environment. It also demonstrated that the bolt can be coated with the smart adhesive material for on‐demand bonding. This design principle opens the door to the development of remotely controllable high‐performance smart underwater adhesives.

Artificial Leaky Integrate-and-Fire Sensory Neuron for In-Sensor Computing Neuromorphic Perception at the Edge.

Neuromorphic perception and computing show great promise in terms of energy efficiency and data bandwidth compared to von Neumann's computing architecture. In-sensor computing allows perception information processing at the edge, which is highly dependent on the functional fusion of receptors and neurons. Here, a leaky integrate-and-fire (LIF) artificial spiking sensory neuron (ASSN) based on a NbOx memristor and an a-IGZO thin-film transistor (TFT) is successfully developed. The ASSN is fabricated mainly through simple sputter deposition processes, showing the prospect of high process compatibility and potential for integration fabrication. The device shows excellent spike encoding ability to deliver the neuromorphic information through spike rate and time-to-first spike. Moreover, in the ASSN, the a-IGZO TFT not only provides the fundamental spike signal computing function of the artificial neuron but also has NO2 gas and ultraviolet (UV) light dual sensitivity to introduce the neuromorphic perception capability. As a result, the ASSN successfully exhibits an inhibitory property under NO2 stimulation while exhibiting an excitatory state under UV light stimulation. Futhermore, self-adaption and lateral regulation circuits between different ASSNs are proposed at the edge in mimicking biological neurons' rich interconnection and feedback mechanisms. The ASSNs successfully achieve self-regulation after a huge response during a burst stimulus. In addition, the neuron transmits a more obvious output when the target-sensitive events occur through the edge internal regulation. The self-adaption and lateral regulation demonstrated in ASSN move an important step forward to in-sensor computing, which provides the potential for a multiscene perception in complex environments.

Energy transfer and luminescent properties of Lu2WO6:Bi3+,Eu3+ red emission phosphor

White light-emitting diodes (W-LEDs) occupy an important role in human life. The lack of red-light emission phosphors makes the packaged W-LEDs have high color temperature and low color rendering index. Herein, Bi3+ and Eu3+ doped Lu2WO6 phosphors with red luminescence were manufactured. The structural properties, luminescent properties and energy transfer processes were investigated systemically. Under ultraviolet light stimulation, blue, green and red light emissions are detected, which stem from (WO6)6-, Bi3+ and Eu3+, respectively. Significantly, the optimal sample of Lu2WO6:0.002Bi3+,0.18Eu3+ presents favorable thermal stability, whose luminescent intensity at 423 K keeps 94% of that at 300 K. Above results unlock that Lu2WO6:Bi3+,Eu3+ samples might have promising application in solid-state lighting field.

Ultraviolet-selective organic phototransistors for low-power skin-inspired nociceptor

Skin-inspired nociceptors are particularly important for future neurorobotic technology. In this work, an artificial skin nociceptor based on ultraviolet (UV)-selective C8-BTBT phototransistors was reported. By using polymethyl methacrylate as an interfacial modification layer, a large number of standing crystals appeared in the C8-BTBT film, and the photo-dark current ratio of the devices exceeded the value of 1010. The main biological synaptic behaviors of the devices under UV light stimuli were also thoroughly investigated. Interestingly, the minimum power consumption per synaptic event (2.45 fJ) is comparable to the energy required by the biological synapses. The biological behavior of the skin-inspired nociceptor was further simulated, such as allodynia, hyperalgesia, and the self-protection behavior under UV light stimulation. Finally, as a proof of concept, the skin-inspired nociceptor was proposed to be integrated with the UV-transmittance modulator to protect against excess UV stimulation, which fully demonstrated its potential applications in bionic electronics technology.

Time-resolved encryption via photochromic and mechanochromic system based on silane-substituted spiropyran

With the continuous progress of forgery and decryption, the traditional static encryption technology is becoming more and more inadequate, which also strongly demands the development of multilevel anti-counterfeiting materials and advanced multi-dimensional encryption strategies and technologies. Here a new strategy to realize time-resolved encryption based on a silane-substituted spiropyran is presented, which exhibits tunable dynamic photochromic features caused by the reversible photochromic and mechanochromic properties with exceptional reversible absorption/luminescence modulation ability both in powder and crystal state. This compound shows excellent photochromic properties, including extremely rapid response time, high contrast color change, high reversibility etc. In addition, the growth of large-size needle-like single crystal by solution evaporation is helpful to further explore the mechanism of grinding discoloration of the compound. What's more, it is possible to modulate the luminescence emission and color change by simply changing the ultraviolet light stimulation time or grinding time, providing fine and adjustable time-related characteristics for the material, which can not only be used for data processing with more extended information, but also be used to construct confidential materials by time-resolved multidimensional encryption and dynamic anti-counterfeiting.

Sensitive acid phosphatase assay based on light-activated specific oxidase mimic activity

Acid phosphatase (ACP) is a key marker in the diagnosis of many diseases. However, exploiting a simple and sensitive sensor for the real-time quantitative analysis of ACP is still challenging. Herein, we attempted to develop a sensitive colorimetric sensing strategy for the detection of ACP based on light-activated oxidase mimic property of carbon dots (CDs). The synthesized CDs were proved to be capable of intrinsic light-activated oxidase mimic activity, which could generate reactive oxygen species to oxidize chromogenic substrate under ultraviolet light stimulation. Interestingly, this light-activated oxidase mimic behavior would be effectively suppressed by the antioxidant ascorbic acid (AA), a product from the hydrolysis of 2-phospho-L-ascorbic acid trisodium (AAP) mediated by ACP. Based on the above property, a facile and sensitive colorimetric sensing method for ACP was developed. Under the optimal conditions, the linear range for ACP 0.1–5.5 U/L, and the detection limit was 0.056 U/L. Compared with conventional nanozyme based ACP assay systems, the catalytic activity of light-activated nanozyme could be conveniently regulated by switching the light on and off, which made it easier to precisely control the extent of the reaction and ensured the accuracy of the assay. In addition, the proposed sensing system would be readout directly by the naked eye or smartphone-based RGB analysis system, and have been successfully applied to analyze diluted in diluted fetal bovine serum and urine samples spiked with ACP. All these results indicated that this approach holds good promise for future applications in clinical analysis and point-of-care (POC) biosensor platforms.

Molecular-Layer-Defined Asymmetric Schottky Contacts in Organic Planar Diodes for Self-Powered Optoelectronic Synapses.

Optoelectronic synapses have been utilized as neuromorphic vision sensors for image preprocessing in artificial visual systems. Self-powered optoelectronic synapses, which can directly convert optical power into electrical power, are promising for practical applications. The Schottky junction tends to be a promising candidate as the energy source for electrical operations. However, fully utilizing the potential of Schottky barriers is still challenging. Herein, organic self-powered optoelectronic synapses with planar diode architecture are fabricated, which can simultaneously sense and process ultraviolet (UV) signals. The photovoltaic operations are facilitated by the built-in potential originating from the molecular-layer-defined asymmetric Schottky contacts. Diverse synaptic behaviors under UV light stimulation without external power supplies are facilitated by the interfacial carrier-capturing layer, which emulates the membranes of synapses. Furthermore, retina-inspired image preprocessing functions are demonstrated on the basis of synaptic plasticity. Therefore, our devices provide the potential for the development of power-efficient and advanced artificial visual systems.

Three-dimensional electrochemical etching by grid ditching for multi-wavelength visible-light emission on porous silicon.

A new approach of three-dimensional electro-chemical etchings both in vertical and lateral current directions on grid ditched Si pn-structures is originally proposed. Lateral etchings on the different ditched zones cause different porosities on porous Si, which emit visible lights of different wavelengths under ultraviolet light stimulation. Therefore, a single Si-based chip is capable of emitting visible light with tunable and multiple wavelengths simultaneously by this new approach. Moreover, the etching conditions on porous Si films and their related wavelengths can be fine-tuned by area sizes. Compared with the conventional method, the new approach provides a new option for multi-wavelength chip design with a precise patterning for porous Si without any mask and photoresist.

Long persistent and photostimulated luminescence properties of Sr2Al2SiO7:Eu2+/Tm3+ phosphors

AbstractA series of Sr2Al2SiO7 phosphors with fixed Eu2+ concentration and various Tm3+ concentrations were synthesized via a high temperature solid state reaction. The structure and luminescence properties of the samples were characterized by X-ray powder diffraction (XRD), photoluminescence (PL) spectra, decay curves, thermoluminescence (TL) glow curves as well as the photostimulated luminescence (PSL) spectra. Sr2Al2SiO7:Eu2+, Tm3+ phosphors exhibited strong green phosphorescence and photostimulated luminescence originating from 4f65d1–4f7 transition of Eu2+ after ultraviolet light stimulation. Deep traps were found by analyses on the phosphorescence decays and thermoluminescence spectra. It was also found that with increasing the time interval between UV excitation turn-off and stimulation turn-on, the photostimulated luminescence became stronger. This phenomenon resulted from the fact that the captured electron was retrapped by the deep traps. Compared with the Tm3+-free sample, it was found that the PSL intensity was strongly enhanced in Tm3+ codoping samples.

Spectral and Temporal Sensitivity of Cone-Mediated Responses in Mouse Retinal Ganglion Cells

The retina uses two photoreceptor types to encode the wide range of light intensities in the natural environment. Rods mediate vision in dim light, whereas cones mediate vision in bright light. Mouse photoreceptors include only 3% cones, and the majority of these coexpress two opsins (short- and middle-wavelength sensitive, S and M), with peak sensitivity to either ultraviolet (360 nm) or green light (508 nm). The M/S-opsin ratio varies across the retina but has not been characterized functionally, preventing quantitative study of cone-mediated vision. Furthermore, physiological and behavioral measurements suggested that mouse retina supports relatively slow temporal processing (peak sensitivity, ∼ 2-5 Hz) compared to primates; however, past studies used visible wavelengths that are inefficient at stimulating mouse S-opsin. Here, we measured the M/S-opsin expression ratio across the mouse retina, as reflected by ganglion cell responses in vitro, and probed cone-mediated ganglion cell temporal properties using ultraviolet light stimulation and linear systems analysis. From recordings in mice lacking rod function (Gnat1(-/-), Rho(-/-)), we estimate ∼ 70% M-opsin expression in far dorsal retina, dropping to <5% M-opsin expression throughout ventral retina. In mice lacking cone function (Gnat2(cpfl3)), light-adapted rod-mediated responses peaked at ∼ 5-7 Hz. In wild-type mice, cone-mediated responses peaked at ∼ 10 Hz, with substantial responsiveness up to ∼ 30 Hz. Therefore, despite the small percentage of cones, cone-mediated responses in mouse ganglion cells are fast and robust, similar to those in primates. These measurements enable quantitative analysis of cone-mediated responses at all levels of the visual system.

Molecular characterization of a CD95 signaling mutant.

To study the intracellular signaling events associated with ligation of the surface receptor CD95. A mutant clone of Jurkat T cells, DD3, which fails to transmit apoptotic signals through CD95, was selected for study. Surface expression of CD95 and the primary nucleotide sequence of CD95, as well as the functional effects of a mutant CD95 molecule found in DD3, were examined. DD3, while exhibiting impaired ability to undergo apoptosis after CD95 ligation, retained the ability to die after ultraviolet light stimulation. A CD95 complementary DNA (cDNA) cloned from DD3 encoded a mutant transmembrane protein lacking the carboxy-terminal "death domain." Western blotting confirmed the presence of both wild-type and mutant CD95 protein in DD3. Transfection of the mutant CD95 cDNA into parental Jurkat cells conferred protection from CD95-mediated apoptosis. A mutant CD95 receptor lacking the cytoplasmic "death domain" can interfere with wild-type receptor function in T cells.

Regional variations in the relative sensitivity to UV light in the mouse retina.

About 3% of all mouse photoreceptors are cones. An earlier electrophysiological study indicated that there were two classes of cone in the mouse retina having peak sensitivities (lambda max) of about 360 nm and 511 nm. Recent immunocytochemical results show there are two types of cones that have distinctive regional segregation patterns. We used regional stimulation of the retina in conjunction with electroretinogram (ERG) flicker photometry to see if the two cone types identified electrophysiologically are regionalized in a fashion suggested by the anatomical results. We find they are. Relative sensitivity to ultraviolet and visible light stimulation qualitatively parallels that predicted by immunocytochemical labelling. One result of this remarkable regionalization of cone types is that the mouse retina is relatively more sensitive to ultraviolet light stimulation when that light is directed toward the ventral half of the retina.

Chronic solar dermatosis--an electronmicroscopic study of the epidermis.

Summary The epidermis from six cases of chronic solar dermatosis (three from the face, and three from the neck), has been examined with the electronmicroscope. There is electronmicroscopic evidence of reduced protein and lipid reserves in the keratinocytes, and of decreased keratin formation. These changes are believed to be caused by poor nutrition as a result of the ultraviolet light-induced changes in the dermis. There is no indication that the keratinocytes. are affected directly by the ultraviolet light. Some melanocytes are large and hyper-functional, probably due to ultraviolet light stimulation, but many are hypo-functional with few or no melanosomes, few cellular organelles, and frequently a deeply indented nucleus. It is considered likely that the ultraviolet light filtering ability of the epidermis is reduced in chronic solar dermatosis because there is less keratin in the stratum corneum and many melanocytes are incapable of producing melanin. Therefore, once chronic solar dermatosis is established, it would predispose to the development of ultraviolet light induced cancers.

Fine Structure of the Nevus Cell

The purpose of this investigation was to characterize the fine structure of the nevus cell and to demonstrate, if possible, a unique premelanin granule. The presence of this granule in the nevus cell would substantiate the relationship between the nevus cell and the melanocyte. Biopsy specimens of dermal nevi with and without ultraviolet light stimulation were studied with an electron microscope and the following conclusions were reached: (1) The fine structure of the nevus cell is comparable to that of the melanocyte. (2) The premelanin granule or melanosome is present in the nevus cell, particularly after prolonged ultraviolet light stimulation. (3) The nevus cell is probably an embryonal cell that can differentiate with appropriate stimuli.